1. Technical Field
The present invention relates to fuel cells and, in particular, the cooling of fuel cells.
2. Background Information
Evaporative cooling of fuel cells is well known in the art. Commonly owned U.S. Pat. No. 3,704,172 to Stedman et al describes the use of evaporative cooling in a fuel cell system. In that system, a porous liquid/vapor barrier is disposed between adjacent fuel cells. Liquid water is directed across one side of the barrier and is partially converted to steam by having a pressure on the other side that is lower than the vapor pressure on the liquid side. As stated in Stedman et al, the vapor pressure at the exit of the vapor side of a liquid/vapor porous barrier is a function of the operating temperature of the fuel cell within which the barrier is located. In Stedman et al the vapor pressure at the exit of the vapor side of the barrier is monitored, and the amount of liquid coolant flow into the cell on the liquid side of the liquid/vapor barrier is controlled as a function of that vapor pressure in order to maintain a predetermined pressure differential between the vapor outlet and the liquid water inlet, thereby maintaining a desired cell temperature.